1. Field of the Invention
The present invention relates to techniques for proactively detecting impending problems in computer systems. More specifically, the present invention relates to a method and apparatus for mitigating quantization effects in telemetry signals while using the telemetry signals to detect impending problems in a computer system.
2. Related Art
Continuous system telemetry is being increasingly used for real-time proactive health monitoring of servers, networks, and peripherals. Continuous system telemetry is typically used in conjunction with pattern recognition techniques to identify patterns in telemetry signals that can indicate whether a computer system is at the onset of degradation. In some computer systems, low-resolution analog-to-digital chips (e.g., 8-bit A/D chips) are used to convert analog telemetry signals into digital telemetry signals. Low-resolution A/D chips can generate digitized telemetry signals that are severely quantized. Hence, values for the quantized telemetry signals are reported in only a few “quantization levels.” Unfortunately, pattern recognition techniques cannot be applied to low-resolution quantized telemetry signals.
One solution to this problem is to use higher-resolution A/D chips. For example, a 12-bit A/D chip provides 16 times more quantization levels than an 8-bit A/D chip. Unfortunately, such higher-resolution A/D chips are expensive, and retrofitting legacy systems that contain low-resolution A/D chips with higher-resolution A/D chips is impractical.
Other solutions involve preprocessing raw telemetry signals to infer the true mean values of the signals. For example, a moving histogram technique or a spectral synthesis technique can be used to mitigate the effects of quantization in computer telemetry signals. The moving histogram technique is described in “Technique for Detecting Changes in Signals that are Measured by Quantization,” by inventors Keith A. Whisnant and Kenny C. Gross (U.S. patent application Ser. No. 10/809,721). The spectral synthesis technique is described in “Method and Apparatus for Removing Quantization Effects in a Quantized Signal,” by inventors Kenny C. Gross, Ramakrishna C. Dhanekula, Eugenio J. Schuster, and Gregory A. Cumberford (U.S. patent application Ser. No. 11/342,057). The above-listed patent applications are hereby incorporated by reference to provide details on how the moving histogram technique and the spectral synthesis technique can be used to mitigate the effects of quantization in computer telemetry signals.
Unfortunately, both of the above-described preprocessing techniques are computationally costly. Although the preprocessing computations can be performed on the computer system that is being monitored, computer system manufacturers are very reluctant to impose such an overhead on a customer's computer system in exchange for electronic prognostics. One solution to this problem is to preprocess the telemetry signals on a remote computer system. In this type of remote-monitoring technique, low overhead can be maintained on the customer's computer system. Unfortunately, telemetry archival becomes more difficult because the telemetry signals must be preprocessed prior to archival (to make possible intelligent data mining of archival telemetry databases).
Because of the problems described above, telemetry signals are sometimes written straight to archive databases with no preprocessing. These raw, quantized signals are then post processed in an offline manner to generate reports for systems identified to be at risk of failure. These offline reports are generated periodically (e.g., every 24 hours). For offline post-processing analyses, compute cost is no longer an issue. The telemetry signals can be retrieved from the telemetry archive, and a moving histogram technique or a spectral synthesis technique (as described above) can be used for real-time online analyses. However, present techniques to “unquantize” quantized telemetry signals still do not provide a desired sensitivity level for the detection of subtle anomalies and avoidance of false alarms.
Hence, what is needed is a method and an apparatus for mitigating quantization effects in a quantized telemetry system without the problems described above.